Objectivity should be attempted when possible, but eliminating subjectivity is impossible unless you want to review an album based on mathematic principles.
When I review genres I hate, it's only because I'm sent the promo. Generally melodeth and pre-post-hard-core- are the unfortunates to fall under the brunt of my wrath.
My favorite review is JayKeeley's bludgeoning of that Madder Mortem album.
I like Boris's reviews of non-thrash/speed/trad, etc., because chances are if he hates it I probably won't like it much eitherunless it's Nevermore or Evergrey. It's probably a lot easier for me to judge the actual sound through his description cause I know him in real life, though.
Abominatrix needs to write more negative reviews; his positive ones are fucking brilliant.